The present invention relates to speed regulation method and apparatus of an asynchronous motor in order to save electricity.
It has generally been found a number of speed regulation method and apparatus in the prior art of asychronous motor, but none of them has been able to be simple, reliable, cheap and high efficent simutanously, and may be carried out is conventional single speed squirrel cage motor. The controllable speed range is quite narrow, as one third of the normal rotating speed or the less, e.g. disclosure in JP-54-7514.